The ANIMAL/BIOCHEMISTRY will be the central resource for carrying out the common ischemia-reperfusion protocols on rabbit hearts, and the preliminary processing of tissues for studies on i) intact muscles, ii) intact ventricular myocytes, iii) isolated mitochondria, and iv) mitochondrial inner membranes. The Director, in consultation with the Leaders, will be responsible for supervision of all of the animal-related needs. We will be responsible for providing post-ischemic tissues for the intact muscle preparation (carried further by the Fluorescence/ Isolated Muscle for the enzymatic digestion of hearts for isolated cardiomyocyte studies for rapid freezing of tissues prior to homogenization and membrane fractionation for the proteomics studies, and for mitochondrial isolation/ inner membrane preparation from fresh tissue. Centralization of these functions will ensure that a reproducible protocol is followed for cross-correlation of the results and that state-of-the-art methods are followed for provision of high quality mitochondrial and membrane preparations to participants with varying degrees of expertise in these areas. Records of the functional changes associated with the heart perfusions will be maintained and accessible to investigators for post hoc correlation with experimental findings, maximizing the information gained while minimizing animal and personnel costs.